The main objectives of the study are to determine the role of Schistosoma hematobium infection and its treatment on anemia and on growth of children. Schistosomiasis is a prevalent disease but its adverse effects on nutritional status have not been well studied. The study design using 1000 primary school children in Kenya will allow a determination to be made of the extent to which this disease is contributing to anemia and retarded physical growth which are known to be common in this area, as well as many parts of Africa. Substudies are planned to investigate other important questions including physical fitness and urinary iron loss in persons with both light and heavy infections. The hematological and growth response to treatment will be assessed, and these results are expected to be useful in determining the priority, the costs, and the feasibility of routine treatment of primary school children as a means of controlling this important disease.